Refrigeration



Aug. 23, 1932. E. T. WILLIAMS REFRIGERATION Filed April 19, 1929 2 Sheets-Sheet l I INVENjW A 1932- E. T. WILLIAMS 1,873,237

REFRIGERATION Filed April 19, 1929 2 Sheets-Sheet 2 MLMWJMM INVENTOR Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE REFRIGERATION Application filed April 19,

My invention relates to refrigeration. More particularly the invention relates to refrigerating systems of the compression type wherein an appreciable quantity of liquid is 6 maintained in the low pressure or expansion side; that is, to the flooded type of system as distinguished from the dry type of system.

Lubrication is necessary to all refrigerating systems of the compression type. My

10 invention is particularly concerned with systems wherein lubricant circulates throughout the refrigerant cycle. It has always been a matter of more or less difficulty to properly lubricate refrigerating systems. The principal difficulty lies in return of the lubricant from the low pressure side to the compressor.

While this does not present so serious a problem with dry systems as with flooded systems,

flooded systems have many advantages over dry systems which more than offset the added difficulties of proper separation of the oil from the refrigerant and return of the same to the compressor.

This invention is particularly applicable to systems wherein the lubricant is of substantially the same specific gravity as the refrigerant or is in solution with the refrigerant. In compression type refrigerating apparatus there are often used such combinations of refrigerant and lubricant which mix and are commonly referred to as working fluid. Heretofore circulation of the socalled working fluid has been accomplished by introducing the fluid, which comprises both refrigerant and lubricant, from the evaporator into the vapor suction line to the compressor. The losses occasioned by the introduction of liquid refrigerant along with the lubricant into the vapor suction line are obvious.

In accordance with this invention a working fluid comprising both refrigerant and lubricant may be used and there is contemplated a system for the return of lubricant to the compressor from the low pressure side which is simple in construction, has no moving parts, insures the return of lubricant without carrying unevaporated refrigerant into the suction line, and which permits the 1929. Serial No. 356,338.

use of a flooded system without impairing the efliciency or operation of such system.

An important feature of my invention is the formation of an intensified foaming zone or space in which, due to ebullition, oil is foamed. In the preferred manner of carrying out my invention I provide an upwardly tapering chamber such that vapor bubbles formed in liquid therein are forced to concentrate. Bubbles leave the liquid through a 00 disengaging surface which is smaller in area than the transverse area of maximum bubble formation within such chamber. This causes an agitation and a distinct foaming which results in carrying foamed oil into the ca suction line.

I may form the evaporator of a compression system so that the evaporator shell itself serves this function but preferably I provide a bell inside the evaporator shell open at the bottom and having a restricted area in the upper portion thereof. The upper part of this bell is connected by a tube of preferably substantially small diameter to the suction conduit leading to the compressor. The bell is partly or wholly submerged in the liquid body Within the evaporator shell so that in operation a restricted gassing space is formed in the upper part thereof. In order to insure that no liquid is carried into the suction line I prefer that the upper part of the bell be placed above the normal surface of liquid inside the evaporator.

Further advantages and the nature of my invention will be fully explained in the following description taken in conjunction with the accompanying drawings showing several forms of the invention and which form a part of the specification.

On the accompanying drawings Fig. 1 is an elevational cross-sectional view of an evaporator embodying the invention, taken on the line 1--1 of Fig. 2 and showing the interior parts of the evaporator in full;

Fig. 2 is a cross-sectional view looking down, taken on the line 22 of Fig. 1 and showing the interior parts of the evaporator in full;

Fig. 3 is an outside view of the evaporator;

Fig. 4 is a cross-sectional view of a moditied form of evaporator embodying the invention.

Referring to the embodiment of the invention shown in Figs. 13, reference character 10 designates the header or shell of the evaporator. This is a cylindrical member closed at both ends and designed to be arranged on a horizontal axis. This shell may be of any shape however, so far as this embodiment of the invention is concerned. Tubes 11 are connected to the header in this embodiment. Each tube has one end connected to the header below the. normal liquid level therein and the other end connected to the header above the normal liquid level whereby the fluid circulation through each tube is in one direction and liquid and gas flow are not in opposition. Other forms of tubing or no tubing may be used intsead of the form of tubing shown. Also extended surface may be added to the shell in the form of fins.

Liquid refrigerant carrying lubricant is supplied to the evaporator through inlet connection 12. A valve 13 controls the supply of liquid refrigerant into the evaporator. The liquid refrigerant is admitted directly into shell 10. Valve 13 is moved to regulate flow of liquid refrigerant by means of a float 14 attached to an arm 15 pivoted at 16. The float 14 is buoyed up by the liquid in the evaporator and serves to maintain a substantially constant level of liquid in the evaporator.

A discharge conduit 17 is formed in a boss 18 and is connected to the suction line of the refrigerating system of which t e evaporator forms a part. The ordinary compresssor and condenser are connected to the evaporator so that gaseous refrigerant is drawn through conduit 17, into the suction line leading to the compressor, is compressed in the compressor, converted to liquid in the condenser and forced back to the evaporator through inlet port 12.

\Vithin the shell 10 is a member 19 which is more or less bell shaped. This member is open at the bottom, tapers upwardly and is connected by a tube 20 to outlet conduit 17. Member 19 is placed so that the upper portion thereof is above the normal liquid level in shell 10 and so that the lower portion is well below the normal liquid level in shell 10. This member provides an oil foaming zone. The oil foams up within bell member 19 and the oil foam is carried through to 20 into the suction line.

In operation:

Heat taken up by the evaporator in order to produce refrigeration causes the formation of gaseous refrigerant which is carried away to the compressor. The evaporation results in a lowering of the liquid level, as a result of which float 14 lowers and opens valve 13 more or less to admit liquid refrigerant into the evaporator. Lubricant is carried along with the refrigerant. Let it be assumed that the lubricant is of substantially the same specific gravity as the refrigerant and mixes with the refrigerant in solution form. IVhen suflieient liquid has been admitted to the evaporator to raise float ll sutliciently, valve 13 is closed.

Assume now that the compressor is started. The vapor pressure in shell 10 is reduced and ebullition occurs in the liquid. Bubbles of refrigerant form and these bubbles rise. Within member 19 is an isolated body of liquid. As the bubbles rise in this isolated body, the taper of member 19 causes the hubbles to move together. This results in an agitation within member 19. A foam of lubricant is formed. The upper part of member 19 becomes filled with the foam. The foam passes through tube 20 and into the suction line.

I believe that the lubricant forms as skin around individual nuclei of refrigerant vapor and that the refrigerant vapor and oil is thus carried upwardly together due to the light weight of the gaseous refrigerant. The foaming is caused by the concentration of the bubbles due to the restricted area of the upward path of flow. However, while I believe this to be the theory, I do not wish to be restricted to any particular theory as to the character of the foam or its formation.

As the ebullition is more intensified, the collection of gas in the upper part of member 19 will force the liquid therein downwardly. This serves to create a liquid head acting on the gase inside member 19 which serves to force the gas through conduit 20.

In Fig. 4, the upwardly tapering part and the shell are combined into one unit 30 which has an upper dome 31 corresponding to the upper part of bell member 19 in Fig. 1. All the bubbles formed in shell 30 are forced to pass to a restricted disengaging surface within dome 31. The liquid level is maintained within this dome by means of the float 32 which is so connected to the inlet valve 13 as to maintain the liquid level at a constricted point. It will be seen that in this embodiment, as well as the previously described embodiment, the cross-sectional area of flow of bubbles upwardly is restricted within a body of liquid refrigerant carrying lubricant. Obviously, the agitation and foaming may be such that there is no definite liquid level.

While I have described several forms of the invention, it will be understood that many forms of apparatus are possiblefor carrying out the invention and that the method of cir culating lubricant herein described is independent of any specific apparatus.

In the foregoing specification the terms oil and lubricant are synonymous.

I claim:

1. The method of circulating lubricant in a refrigerating system which comprises boiling a body of liquid refrigerant with lubricant therein, constricting the upward path of flow of the boiled refrigerant in said body to foam the lubricant, lifting the lubricant due to foaming thereof and removing the lifted lubricant from the presence of said body.

2. The method of circulating lubricant in a refrigerating system which comprises heating a body of liquid refrigerant with lubricant therein to form bubbles of gaseous refrigerant in said body, constricting the upward path of flow of the bubbles in the liquid body to agitate the body and foam the lubricant, lifting the lubricant due to foaming thereof and removing the lifted lubricant from the presence of said body.

3. The method of circulating lubricant in a refrigerating system including a compressor, a condenser and an evaporator connected in a circuit containing refrigerant and lubricating fluids which comprises maintaining an appreciable quantity of liquid refrigerant in the evaporator, isolating a body of liquid in the evaporator, constricting upward passage of gas in said body to produce foaming, lifting the lubricant due to the foaming and drawing the lifted lubricant out of the evaporator toward the compressor.

4. In compression refrigerating apparatus of the flooded evaporator type having a working fluid comprising a solution of refrigerant and lubricant, the method of returning refrigerant gas and lubricant from the evaporator to the compressor which comprises constricting the upward path of flow of gas bubbles in the evaporator to foam lubricant at the liquid surface therein, and conducting the lubricant foam to the compressor through the vapor suction line.

5. In compression type refrigerating apparatus including a flooded type evaporator, a member in said evaporator enclosing a substantially cone-shaped chamber open at the bottom below the normal level of liquid refrigerant in the evaporator and communicatlng at its upper end with the vapor suction line.

6. In compression type refrigerating apparatus including a flooded t pe evaporator, means forming an upwar ly converging chamber within said evaporator open at the bottom below the normal level of liquid refrigerant in the evaporator and connected from its upper portion above the normal 1i uid level to the vapor suction line.

7. In compression type refrigerating apparatus including a flooded type evaporator, a member within said evaporator enclosing a chamber open at the bottom below the normal level of liquid refrigerant in the evaporator and converging upwardly to the liquid surface, the upper part of said chamber being above the normal liquid level and communicating with the vapor suction line.

8. A flooded type evaporator having an upwardly converging chamber open at the bottom below the normal level of liquid refn'gerant in the evaporator and connected from its upper portion above the normal liquid level to the vapor outlet.

9. A flooded type evaporator having a substantially conical chamber open at the bottom below the normal level of liquid refrigerant in the evaporator and connected from its upper end above the normal liquid level to the vapor outlet.

10. A flooded type evaporator having a chamber open at the bottom below the normal level of liquid refrigerant in the evaporator and connected from its upper portion above the normal liquid level to the vapor outlet, said chamber having a greater horizontal area at the bottom than at the surface of the liquid refrigerant.

11. In compression type refrigerating apparatus, a flooded type evaporator, a mixture of refrigerant and lubricant in said evaporator, means within said evaporator defining a chamber open at the bottom below the normal level of liquid in said evaporator and converging upwardly to a point above the surface of the liquid, and a connection from the upper partof said chamber to the vapor suction line.

12. In a flooded type evaporator, means for constricting the upward path of flow of refrigerant bubbles to cause foaming of lubricant at the surface of liquid refrigerant in the evaporator, and means for withdrawing the foam from said evaporator.

13. In a flooded type evaporator, a mixture of liquid refrigerant and lubricant, means for constricting the upward path of flow of the refrigerant bubbles through said mixture to cause foaming of the lubricant at the surface, and means for withdrawing the foam from said evaporator.

In testimony whereof I have aflixed my signature.

EDWARD T. WILLIAMS. 

